Those are "
master walls"
that only disappear (or rather become transparent and allow you to walk through them) when you have mastered the hold, i.e. when you have finished the hold by exiting through the hold-ending stairs *and* when you have solved every secret room in the hold.
In other words, just ignore it for now and come back once you've done the above. Those walls are meant to block access to content that only those who have mastered the hold should see, as kind of a bonus...
np: Styrofoam - Anything (ft. Bent Van Looy + Miki) (Nothing's Lost)
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"
I'm not anti-anything, I'm anti-everything, it fits better."
- Sole
R.I.P. Robert Feldhoff (1962-2009)
